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Abstract:

A method of routing multicast traffic, suitable for use in a network
comprising a router node connected to a first data network and to a
second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, is provided. The method comprises: receiving a first message
from the user equipment at the router node, the first message requesting
membership of a first multicast group having a first multicast address;
and inhibiting receipt of multicast traffic having the first multicast
address from at least the second data network by the user equipment,
dependent upon a determination as to whether the first message may relate
to a multicast address in the first network.

Claims:

1. A method of routing multicast traffic, suitable for use in a network
comprising a router node connected to a first data network and to a
second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, the method comprising: receiving a first message from the user
equipment at the router node, the first message requesting membership of
a first multicast group having a first multicast address; and inhibiting
receipt of multicast traffic having the first multicast address from at
least the second data network by the user equipment, dependent upon a
determination as to whether the first message may relate to a multicast
address in the first network.

2. The method according to claim 1, the method further comprising
inhibiting receipt of multicast traffic having the first multicast
address from the first data network by the user equipment, dependent upon
the determination as to whether the first message may relate to a
multicast address in the first network.

3. The method according to claim 1, wherein determining whether or not
the first message may relate to a multicast address in the first network
is performed at least in part by: receiving an indication from the user
equipment indicating that the user equipment has a capability to receive
a multicast service using a multicast address in the first network; and
determining that the first message may relate to a multicast address in
the first network dependent on receipt of the indication.

4. The method according to claim 1, wherein determining whether or not
the first message may relate to a multicast address in the first network
is performed at least in part by: sending a second message from the
router node to a serving node of the first data network, the second
message requesting authorization to join the first multicast group; and
determining that the first message may relate to a multicast address in
the first network dependent upon receipt of authorization to join the
first multicast group from the serving node of the first data network.

5. The method according to claim 1, the method further comprising
determining whether or not the first message may relate to a multicast
address in the first network by determining whether or not the first
multicast address is present in a list of addresses of multicast groups
relating to the first data network.

6. The method according to claim 5, wherein said list is held at the
router node.

7. The method according to claim 5, wherein said list is held in a
database on a different node to which the router node has access.

8. The method according to claim 4, the method further comprising sending
the second message dependent on a determination that the first multicast
address is not present in a list of addresses of multicast groups
relating to the first data network.

9. The method according to claim 1, wherein the router node is a wireless
router node.

10. The method according to claim 4, wherein the second message comprises
an indication that the second message is originated by a wireless router
node.

11. The method according to claim 4, wherein the second message comprises
an indication that a multicast service should not be provided.

12. The method according to claim 1, wherein multicast traffic from the
first network data network is provided by a Broadcast Multicast Service
Centre.

13. The method according to claim 1, the method further comprising
discarding traffic having the first multicast address received from at
least the second data network, dependent upon the determination that that
the first message may relate to a multicast address in the first network.

14. The method according to claim 1, the method further comprising
sending a message from the router node to the user equipment rejecting
membership of the multicast group, dependent upon the determination that
the first message may relate to a multicast address in the first network.

15. The method according to claim 1, wherein said inhibiting of receipt
of multicast traffic having the first multicast address from at least the
second data network by the user equipment comprises not sending a message
requesting membership of a first multicast group having a first multicast
address.

16. The method according to claim 1, wherein the router node does not
allow the user equipment to join the Multicast Broadcast Multimedia
Service in response to receipt of the first message.

17. The method according to claim 1, wherein the router node is a Home
Node B.

18. The method according to claim 1, wherein the first data network
comprises a cellular wireless core network.

19. The method according to claim 1, wherein the second data network
comprises a residential data network.

20. The method according to claim 1, wherein the second data network
comprises an enterprise data network.

21. A router node, suitable for connection to a first data network and to
a second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, the router node being arranged to: receive a first message
from the user equipment, the first message requesting membership of a
first multicast group having a first multicast address; and inhibit
receipt of multicast traffic having the first multicast address from at
least the second data network by the user equipment, dependent upon a
determination that the first message may relate to a multicast address in
the first network.

22. A method of routing multicast traffic, suitable for use in a network
comprising a router node connected to a first data network and to a
second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, the method comprising: receiving a first message from the user
equipment at the router node, the first message requesting membership of
a first multicast group having a first multicast address; and inhibiting
receipt of multicast traffic having the first multicast address from at
least the second data network by the user equipment, dependent upon a
determination as to whether the user equipment is capable of supporting
services using a multicast address in the first network.

23. A router node, suitable for connection to a first data network and to
a second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, the router node being arranged to: receive a first message
from the user equipment, the first message requesting membership of a
first multicast group having a first multicast address; and inhibit
receipt of multicast traffic having the first multicast address from at
least the second data network by the user equipment, dependent upon a
determination as to whether the user equipment is capable of supporting
services using a multicast address in the first network.

Description:

TECHNICAL FIELD

[0001] The present invention relates generally to data networks, and more
specifically, but not exclusively, to a method and apparatus for
improving management of multicast traffic in wireless networks.

BACKGROUND ART

[0002] Multicast traffic is typically a form of point to multi-point
traffic, in which a user typically indicates an interest in receiving the
traffic to a data network. The data network then may authorise the
receipt of the traffic by the user equipment. Multicast traffic may be
carried by many types of data network, including wireless networks, to
provide services such as Multimedia Broadcast Multicast Service (MBMS).
Wireless networks, in which a user equipment (UE) such as a mobile
handset communicates via wireless links to a network of base stations or
other wireless nodes connected to a telecommunications network, have
undergone rapid development through a number of generations of radio
access technology. The initial deployment of cellular systems using
analogue modulation has been superseded by second generation (2G) digital
cellular systems such as GSM (Global System for Mobile communications),
typically using GERA (GSM Enhanced Data rates for GSM Evolution Radio
Access) radio access technology, and these systems have themselves been
replaced by or augmented by third generation (3G) digital systems such as
UMTS (Universal Mobile Telecommunications System), using the UTRA
(Universal Terrestrial Radio Access) radio access technology. Multimedia
traffic may typically be carried by 2G and 3G systems.

[0003] Conventional macro-cellular wireless base stations may serve a
relatively large area in which there are a large number of customer
premises and users. In order to improve capacity and coverage, and to
provide additional services to users, Femtocell systems have been
developed, which typically employ wireless router nodes which are
typically low power base stations which may be sited on a customer's
premises, typically residential premises, with a typically small area of
coverage. A femtocell base station may be self-installed by a customer,
and it may typically be connected by backhaul through a telecommunication
network to a public data network and to a mobile operator's core network.
A femtocell base station operating using UTRA radio access technology in
a UMTS system may be referred to as an HNB (Home Node B).

[0004] A femtocell may also be used to connect a user equipment to a local
network, such as a residential network or enterprise network, using a
service known as Local Internet Protocol Access (LIPA). Typically, the
connection will not use a cellular wireless operator's core network. This
may, for example, allow a user to download content from a local network
and for example to connect to internet protocol enabled devices in the
home.

[0005] Multimedia Broadcast Multicast Service (MBMS) is a service offered
typically by a cellular wireless operator, by which content may be
multicast to a group of users, the group typically having an multicast
address. Membership of the group may typically be managed by a protocol
known as Internet Group Management Protocol (IGMP) or Multicast Listener
Discovery (MLD). Some types of femtocell base station, such as for
example some types of Home Node B, may be not be enabled to offer MBMS.

DISCLOSURE OF INVENTION

Technical Problem

[0006] The protocol, such as IGMP or MLD, used to manage group membership
for services provided by a cellular operator's network, may also be used
at a femtocell to manage group membership for local access services
offered using LIPA. This may lead to operational problems given that the
two networks are administered by different authorities. For example, if
the same multicast address is used for both a group relating to the
cellular operator's MBMS services and for local services using LIPA,
unexpected traffic may result.

Solution to Problem

[0007] In accordance with a first aspect of the present invention, there
is provided a method of routing multicast traffic, suitable for use in a
network comprising a router node connected to a first data network and to
a second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, the method comprising:

[0008] receiving a first message from the user equipment at the router
node, the first message requesting membership of a first multicast group
having a first multicast address; and

[0009] inhibiting receipt of multicast traffic having the first multicast
address from at least the second data network by the user equipment,
dependent upon a determination as to whether the first message may relate
to a multicast address in the first network.

[0010] This has an advantage that receipt of multicast traffic from the
second data network is inhibited at least in the case where the first
message may relate to a multicast address in the first network.

[0011] Preferably, the method further comprises inhibiting receipt of
multicast traffic having the first multicast address from the first data
network by the user equipment, dependent upon the determination as to
whether the first message may relate to a multicast address in the first
network. This has an advantage that receipt of multicast traffic is
inhibited at least in the case where the first message may relate to a
multicast address in the first network, and a further advantage that
implementation may be simpler since multicast traffic from both the first
and second data networks may be inhibited.

[0012] In an embodiment of the invention, determining whether or not the
first message may relate to a multicast address in the first network is
performed at least in part by:

[0013] receiving an indication from the user equipment indicating that the
user equipment has a capability to receive a multicast service using a
multicast address in the first network; and

[0014] determining that the first message may relate to a multicast
address in the first network dependent on receipt of the indication.

[0015] This has an advantage that if it is determined that the user
equipment may not have a capability to receive a multicast service using
a multicast address in the first network, it may be determined that it is
not be necessary to inhibit receipt of multicast traffic from the second
data network.

[0016] In an embodiment of the invention, determining whether or not the
first message may relate to a multicast address in the first network is
performed at least in part by:

[0017] sending a second message from the wireless node to a serving node
of the first data network, the second message requesting authorisation to
join the first multicast group; and

[0018] determining that the first message may relate to a multicast
address in the first network dependent upon receipt of authorisation to
join the first multicast group from the serving node of the first data
network. This has an advantage that an up-to-date indication may be
determined as to whether or not the first data network uses the first
multicast address, that is to say whether or not the first message may
relate to a multicast address in the first network.

[0019] In an embodiment of the invention, the method comprises determining
whether or not the first message may relate to a multicast address in the
first network by determining whether or not the first multicast address
is present in a list of addresses of multicast groups relating to the
first data network. This has an advantage that a message need not be sent
to a serving node of the first data network.

[0020] In an alternative, said list is held at the router node. This has
an advantage that signalling to another node may be reduced.

[0021] In another alternative, said list is held in a database held on a
different node to which the router node has access. This has an advantage
that a database need not be maintained at the router node.

[0022] The method may comprise sending the second message dependent on a
determination that the first multicast address is not present in a list
of addresses of multicast groups relating to the first data network. This
has the advantage that it may be determined that the first data network
uses the first multicast address, that is to say that the first message
may relate to a multicast address in the first network, in the case that
the list is out-of-date.

[0023] Preferably, the router node is a wireless router node. Aspects of
the invention are particularly applicable to a wireless router node,
since a user equipment may be connected to the wireless node and request
membership of a multicast group.

[0024] The second message, in an embodiment of the invention, comprises an
indication that the second message is originated by a wireless router
node. This has an advantage that the server node may determine that the
request is for authorisation in order to avoid a clash with a multicast
address of a second data network.

[0025] The second message, in an embodiment of the invention, comprises an
indication that a multicast service should not be provided. This has an
advantage that the server node may determine that the request is for
authorisation in order to avoid a clash with a multicast address of a
second data network and accordingly not provide a multicast service.

[0026] Preferably, multicast traffic from the first network data network
is provided by a Broadcast Multicast Service Centre.

[0027] The method may comprise discarding traffic having the first
multicast address received from at least the second data network,
dependent upon the determination that the first message may relate to a
multicast address in the first network. This has an advantage that
traffic having the first multicast address received from at least the
second data network may not be routed to the user equipment, so
inhibiting receipt of the traffic by the user equipment.

[0028] Alternatively, or in addition, the method comprises sending a
message from the router node to the user equipment rejecting membership
of the multicast group, dependent upon the determination that a multicast
group of the first data network has the first multicast address. This has
an advantage of inhibiting receipt of the traffic having the first
multicast address by the user equipment.

[0029] In an embodiment of the invention, inhibiting of receipt of
multicast traffic having the first multicast address from at least the
second data network by the user equipment is implemented by not sending a
message requesting membership of a first multicast group having a first
multicast address. This has an advantage that the inhibiting of receipt
of multicast traffic may be efficiently achieved.

[0030] The router node may be configured so as not to allow the user
equipment to join the Multicast Broadcast Multimedia Service in response
to receipt of the first message. This has an advantage of inhibiting
receipt of the traffic having the first multicast address by the user
equipment.

[0033] The second data network may comprise a residential data network.

[0034] Alternatively, the second data network may comprise an enterprise
data network.

[0035] In accordance with a second aspect of the invention there is
provided a router node, suitable for connection to a first data network
and to a second data network, the router node having a capability to
route multicast traffic from the first and second data networks to a user
equipment, the router node being arranged to:

[0036] receive a first message from the user equipment, the first message
requesting membership of a first multicast group having a first multicast
address; and

[0037] inhibit receipt of multicast traffic having the first multicast
address from at least the second data network by the user equipment,
dependent upon a determination that the first message may relate to a
multicast address in the first network.

[0038] In accordance with a third aspect of the invention there is
provided a method of routing multicast traffic, suitable for use in a
network comprising a router node connected to a first data network and to
a second data network, the router node having a capability to route
multicast traffic from the first and second data networks to a user
equipment, the method comprising:

[0039] receiving a first message from the user equipment at the router
node, the first message requesting membership of a first multicast group
having a first multicast address; and

[0040] inhibiting receipt of multicast traffic having the first multicast
address from at least the second data network by the user equipment,
dependent upon a determination as to whether the user equipment is
capable of supporting services using a multicast address in the first
network.

[0041] In accordance with a fourth aspect of the invention, there is
provided a router node, suitable for connection to a first data network
and to a second data network, the router node having a capability to
route multicast traffic from the first and second data networks to a user
equipment, the router node being arranged to:

[0042] receive a first message from the user equipment, the first message
requesting membership of a first multicast group having a first multicast
address; and

[0043] inhibit receipt of multicast traffic having the first multicast
address from at least the second data network by the user equipment,
dependent upon a determination as to whether the user equipment is
capable of supporting services using a multicast address in the first
network.

[0044] Further features and advantages of the invention will be apparent
form the following description of preferred embodiments of the invention,
which are given by way of example only.

BRIEF DESCRIPTION OF DRAWINGS

[0045] FIG. 1 is a schematic diagram showing a network according to an
embodiment of the invention;

[0046] FIG. 2 is a schematic diagram showing a network according to an
embodiment of the invention;

[0047] FIG. 3 is a schematic diagram showing transmission of messages
according to an embodiment of the invention;

[0048] FIG. 4 is a schematic diagram showing a flow diagram according to
an embodiment of the invention;

[0049] FIG. 5 is a schematic diagram illustrating a principle of operation
that may be used by embodiments of the invention;

[0050] FIG. 6 is a schematic diagram showing transmission of messages, in
a case where there is a potential clash of multicast addresses, according
to an embodiment of the invention;

[0051] FIG. 7 is a schematic diagram showing transmission of messages, in
a case where there unlikely to be a clash of multicast addresses,
according to an embodiment of the invention;

[0052] FIG. 8 is a schematic diagram showing transmission of messages
according to an embodiment of the invention;

[0053] FIG. 9 is a schematic diagram showing transmission of messages
according to an embodiment of the invention; and

[0054] FIG. 10 is a schematic diagram showing transmission of messages
according to an embodiment of the invention.

MODE FOR THE INVENTION

[0055] By way of example embodiments of the invention will now be
described in the context of a network including a Home Node B (HNB)
wireless router node operating using UTRA radio access technology in a
UMTS system, connected to both a data network comprising a cellular
wireless core network and a data network comprising a residential or
enterprise network. However, it will be understood that this is by way of
example only, and that other embodiments may involve other types of data
networks, and a router node using for example other access technologies
such as IEEE802.16 Wimax systems; embodiments are not limited to using a
particular access technology, or to wireless access technology.

[0056] Embodiments of the invention will now be described with reference
to the network illustrated by FIG. 1.

[0057] FIG. 1 illustrates a network, in which a femtocell wireless router
node, known as Home Node B (HNB) 2, is connected to two data networks: a
first data network comprising a mobile operator's core network 5, and a
second data network comprising a residential/enterprise network 6. A user
equipment 4 is in the area of coverage of the Home Node B 2 (typically at
the user's premises) and is connected by a wireless link to the Home Node
B 2. Multicast traffic may be provided to the user equipment via the Home
Node B, from the mobile operator's core network 5, typically Multimedia
Broadcast Multicast Service (MBMS) traffic, or from the
residential/enterprise network 6, typically routed using Local Internet
Protocol (LIPA) routeing. The residential/enterprise network may be
referred to as the LIPA network.

[0058] In the network of FIG. 1, it is possible that a multicast address,
used to route the multicast traffic, may be allocated to both the
residential/enterprise network and the mobile operator's core network.
This is because there may be little or no coordination of multicast
address allocation between the operator of the residential/enterprise
network and the mobile operator's network. This may lead to unwanted
traffic and an unsatisfactory user experience. There may be, for example,
a collision between multicast groups for MBMS services and LIPA routed
traffic.

[0059] Multicast traffic is typically routed in response to a request from
a user. In the case of MBMS, the request typically takes the form of a
request for membership of a multicast group, the group having a multicast
address. A serving node, typically in the mobile operator's core network,
may authorise the user equipment to join the multicast group. The
authorisation may be, for example, dependent on a subscription to a MBMS
service.

[0060] A Home Node B 2 may not be enabled to provide a MBMS service.
Nevertheless, it is advantageous that the Home node B 2 be capable of
providing a multicast service to a user equipment based on traffic
originating from the residential/enterprise network. However, if a user
equipment sends a request to join a multicast group relating to a MBMS
service that shares a multicast address with the residential/enterprise
network, unwanted traffic may result.

[0061] According to a first embodiment of the invention, a first message
is received from the user equipment 4 at the Home Node B 2 requesting
membership of a first multicast group having a first multicast address.
The multicast group may be associated with a service to which the user
equipment has subscribed, and the user equipment may, for example have
moved from an area of coverage of a mobile operator's regular
macro-cellular network into the area of coverage of the Home Node B. The
macro-cellular network does not typically offer Local IP Access (LIPA)
services, and so the user may have been receiving, for example, a MBMS
service with no problems of multicast address clashes. However, as the
user equipment has now connected to the HNB 2, which has connections to
both the mobile operator's core network 5 and also connections to a
residential or enterprise network 6, according to the first embodiment
the Home Node B 2 sends a message to a serving node of the cellular
operator's core network 5 requesting authorisation to join the first
multicast group. This message is intended to determine whether or not the
first multicast address is used by the cellular operator's core network
5, that is to say whether the first message may relate to a multicast
address in the cellular operator's core network; if authorisation to join
the group is received, this is taken as a determination that the cellular
operator's core network uses the first address.

[0062] If it is determined that the cellular operator's core network uses
the first address, that is to say the first message may relate to a
multicast address in the cellular operator's core network, then the
receipt by the user equipment of multicast traffic having the first
multicast address from the residential or enterprise network 6, that is
to say LIPA traffic having the first multicast address, is inhibited.
This inhibition may involve not sending a message to the residential or
enterprise network 6 requesting membership of the first multicast group
having the first multicast address. This inhibition may alternatively, or
in addition, involve discarding the traffic at the Home node B 2, that is
to say by not routeing the LIPA traffic. In this way, a clash is avoided,
and MBMS traffic may continue to be routed, where the capabilities of the
Home Node B allow this. The Home Node B 2 may also send a message to the
user equipment 4 rejecting membership of the multicast group.

[0063] If, however, it is determined that the cellular operator's core
network 5 does not use the first address, that is to say the first
message may not relate to a multicast address in the cellular operator's
core network, then the receipt by the user equipment of multicast traffic
having the first multicast address from the residential or enterprise
network, that is to say LIPA traffic having the first multicast address,
is not inhibited, since in this case there is unlikely to be a conflict
of multicast addresses. In this case, a message may be sent to the
residential or enterprise network 6 requesting membership of the first
multicast group having the first multicast address.

[0064] According to a second embodiment of the invention, a similar
determination is carried out as to whether or not the cellular operator's
core network 5 uses first multicast address, that is to say whether the
first message may relate to a multicast address in the cellular
operator's core network. However, in the second embodiment, if it is
determined that the cellular operator's core network 5 uses the first
address, that is to say the first message may relate to a multicast
address in the cellular operator's core network, then the receipt by the
user equipment of multicast traffic having the first multicast address
from the residential or enterprise network, that is to say LIPA traffic
having the first multicast address, is inhibited, as in the first
embodiment, but also receipt of multicast traffic from the operator's
core network having the first multicast address is inhibited. This
inhibition may involve discarding the traffic at the Home node B 2, that
is to say by not routeing the traffic, or it may be by sending a message
to the user equipment rejecting membership of the requested multicast
group. Alternatively or additionally, the inhibition may involve sending
a message to the serving node of the mobile operator's core network
indicating that membership of the multicast group is not required. This
message may be in the form of an indication that the authorisation
request is for the purposes of determining whether a multicast address is
used by the mobile operator's core network for the delivery of an MBMS
service.

[0065] In this way, a clash is avoided. The user may go back into the area
of coverage of the macro-cellular network to continue with MBMS service.

[0066] Variants of the first and second embodiments are possible, in which
the determination that a multicast group of the cellular operator's core
network uses the first multicast address, that is to say whether the
first message may relate to a multicast address in the cellular
operator's core network, is made by determining whether or not the first
multicast address is present in a list of addresses of multicast groups
relating to the first data network. The list may be held at the Home Node
B 2 or held in a database in a different node to which the Home Node B 2
has access. These approaches have the advantage that signalling may be
reduced. Receipt of traffic having the first multicast address from
either or both data networks may be inhibited by not sending the request
to join the multicast group to the respective network or networks.
Alternatively, the methods of inhibiting receipt of traffic described in
connection with the first and second embodiments may be employed.

[0067] In further variants of the first and second embodiments of the
invention, it is determined whether the first message may relate to a
multicast address in the mobile operator's core network at least in part
by receiving an indication from the user equipment indicating that the
user equipment has a capability to receive a multicast service, for
example MBMS, using a multicast address in the first network. If no such
indication is received, then traffic from the LIPA network may not be
inhibited. However, if an indication is received, then a determination as
to whether a multicast group of the mobile operator's core network may
use the first multicast address may proceed, according to the methods
described in connection with the first or second embodiments.
Alternatively, traffic from the LIPA network may be inhibited on the
basis of receiving the indication from the user equipment.

[0068] It is possible in a further variant to send the message requesting
authorisation dependent on the multicast address not being on the list,
as a form of double checking.

[0069] Embodiments of the invention will now be described in more detail,
and further embodiments will also be described.

[0070] FIG. 2 illustrates an example of the network of FIG. 1 shown in
more detail. The mobile operator's core network 5 may comprise a Home
Node B GateWay (HNB GW) 8, a Gateway General Packet Radio Service Support
Node (GGSN) 10, a Serving GPRS Support Node (SGSN) 16 and a Broadcast
Multicast Service Centre (BM-SC) 14. The BM-SC 14 may be the serving node
in mobile operator's core network that authorises membership of a
multicast group. The mobile operator's core network may be connected to a
Public Data Network (PDN) 12, typically giving Internet access. The HNB 2
is also connected via a Local GateWay (L-GW) 18 to a local network 20,
that may comprise parts of a residential or enterprise network. Routeing
of traffic via the L-GW 18 from the residential/enterprise network
typically uses LIPA.

[0071] Multicast applications receive IP traffic that is routed based on
an Internet Protocol (IP) multicast address. In order to receive
multicast traffic from a mobile operator's core network, a user equipment
4 may be required to have membership of a multicast group having a
multicast address. Multicast group membership is managed and indicated by
the UE to the network by means of a protocol called the "Internet Group
Mangement Protocol" (IGMP) or "Multicast Listener Discovery" (MLD).

[0072] Typically, the gateway, such as a GGSN 10 responsible for
forwarding IP packets from a public data network (PDN) 12 to the user
equipment 4 receives this IGMP/MLD message and determines whether to
provide multicast traffic to the UE 4 by means of multicast mode MBMS,
dependent upon whether or not multicast service is authorized by the
operator of the network proving the multicast traffic. This decision is
taken based upon interaction with between the BM-SC 14 and the GGSN 10
using a reference point known as Gmb.

[0073] LIPA is a form of network connection particularly for 3GPP access
such as UTRAN. In LIPA IGMP may be used to allow multicast routing
between the UE and a residential or enterprise network directly, that is
to say typically not using the mobile operator's core network. This is
preferable to permit multicast traffic used for service discovery, so the
UE 4 can find home services using e.g. Universal Plug and Play (UPnP) or
potentially also make use of multicast applications present in the
enterprise or residential network.

[0074] However, it is possible that the same multicast address may be used
by both the residential/enterprise network and the mobile operator's core
network. This may lead to unwanted traffic and an unsatisfactory user
experience. That is to say, there may be a collision between Multicast
groups for operator services and LIPA routed traffic.

[0075] A UE 4 may normally use a multicast service while under 3G access,
using multicast mode MBMS, or under any access (GERAN, UTRAN or LTE) via
an external PDN. The multicast MBMS is typically associated with a
multicast group, and the multicast group is associated with a particular
IP address (that we will refer to as G). If the same group G is offered
by the local network (residential or enterprise network) for example for
the purposes of service discovery in the residential or enterprise
network, the UE may join the group G via IGMP and get unexpected traffic
via multicast from the same group. This could cause the application that
uses MBMS multicast delivery mode to fail or at the very least to behave
unexpectedly.

[0076] This is a particular problem, since user equipments are typically
not aware whether the packet data protocol (PDP) context (i.e the
connection) that they use in order to send a IGMP/MLD join request is
"broken out" for LIPA. Typically, the UE 4 activates a general purpose
PDP context if one is not already established. The UE 4 then typically
sends an IGMP (IPv4) or MLD (IPv6) Join message over the default PDP
context to signal its interest in receiving a particular multicast MBMS
bearer service identified by an IP multicast address.

[0077] Typically, MBMS specifications do not impose restrictions on the
PDP context that will be used in order to transport the IGMP/MLD Join
message that will be used to activate the MBMS multicast delivery mode
transmissions.

[0078] It is a problem to avoid the situation in which the UE 4 receives
data inappropriately from group G that is used in the residential or
local enterprise network when it expects this as an operator, i.e.
cellular network operator, MBMS service. Regarding the operator MBMS
service, the UE 4 can request membership of a group by means of IGMP/MLD
and this will be handled either by means of MBMS multicast mode, or, if
not authorised, the IGMP request will simply be ignored.

[0079] Regarding LIPA, the residential or local enterprise network where
the IP traffic egresses (reference point Gi) is under the direct control
of the user or enterprise network administrator, potentially
independently of the mobile network operator, therefore there may be
possible for a user to configure a IP multicast group which clashes with
existing IP multicast groups allocated for MBMS services.

[0080] Aspects of the present invention provide a solution to this problem
by at least providing a mechanism to prevent IP multicast group
collisions. Before the HNB 2 proceeds to route multicast traffic for a
group G to the UE, it first checks to determine whether, in the
operator's core network (that is to say typically the mobile operator's
core network, not using LIPA) the group G is already supported for MBMS
services.

[0081] According to an embodiment of the invention, the HNB 2 sends a
message to a serving node of the operator's core network requesting
authorisation to join a multicast group having a first multicast address.
That is to say, the HNB initiates a Gmb MBMS Authorization Request. If
the group exists and authorization can be obtained, then the group that
the UE requests from the LIPA access via IGMP/MLD is not routed to the
UE. Preferably, the HNB does not employ the MBMS Registration Procedure,
so multicast traffic will not be initiated by the BS-MC 14.

[0082] The UE 4 is still able to join multicast groups that are not used
as MBMS multicast mode services in the LIPA network; this is not blocked
by the HNB. For example, the UE 4 may join multicast based service
discovery protocol groups that are not used for MBMS services.

[0083] The functionality required in the HNB 2 and L-GW 18 is effectively
a "filter" that will route IGMP/MLD join requests (that is to say
messages requesting membership of a multicast group) typically only when
it receives indication from the network that the group that the UE 4
attempts to join is not used for MBMS services.

[0084] FIG. 3 shows a typical interaction between the HNB 4 and an
operator's core network in order to determine whether a given IGMP/MLD
join message will collide with an existing multicast mode MBMS service.

[0085] Step 1 shows the conventional set up of a connection (PDP context)
between the UE 4 and the L-GW 18 with LIPA activated. The UE is unaware
of the fact that the PDP context has LIPA activated.

[0086] At step 2, the UE 4 sends a message requesting authorisation to
join a multicast group to a serving node of the operator's core network,
typically the BM-SC 14, that is to say the user equipment initiates an
IGMP/MLD join message in order to initiate MBMS multicast mode.

[0087] The HNB 2 attempts to verify whether the group exists and the UE 4
is authorized to use it in the macro network. Potentially this
verification can optionally be triggered only when the UE 4 has indicated
that it has MBMS capability in its MS Network Capabilities. This may be
accomplished by using the Gmb interface to a serving node of the mobile
operator's network, typically the BM-SC 14, or alternatively the serving
node may be a statically defined Authorisation Server in the Public Land
Mobile Network (PLMN), that is to say the mobile operator's network, that
implements the Gmb authorization function of the BM-SC 14. The IP address
of the BM-SC 14 or Authorisation Server is preferably statically
configured in the HNB 2. The HNB 2 may preferably identify itself by
setting in the the Gmb Authorisation request an identifier indicating
that this request is performed by HNB (instead of GGSN) and is
authorization in order to avoid clashes due to LIPA.

[0088] If the serving node authorizes this use, the HNB 2 assumes that
there is such a group existing and inhibits receipt of traffic by the
user equipment on the requested group from the LIPA network, that is to
say the residential/enterprise network.

[0089] In a variant of the embodiment, a message is sent from the HNB 2 to
the user equipment 4 rejecting membership of the multicast group,
dependent upon the determination that a multicast group of the operators
network uses the multicast address of the group. In a specific example,
the HNB 2 may inhibit traffic to the UE 4 by sending a "Request MBMS
Context Activation Reject" message in order to inform the UE that MBMS is
not supported.

[0090] If on the other hand, the authorization is denied in this step, the
HNB 2 does route multicast traffic of the requested group to the UE 4.

[0091] According to a further embodiment of the invention, the HNB 2
determines whether or not a multicast group of the mobile operator's core
network has the first multicast address by determining whether or not the
first multicast address is present in a list of addresses of multicast
groups relating to the first data network. Preferably, the list is held
at the HNB 2, or in a database to which the HNB 2 has access. For
example, the operator may list multicast addresses of a set of MBMS
multicast mode service groups (popular ones or those used by the owner of
the HNB 2) to prevent collisions with these multicast groups.

[0092] It has been seen that embodiments of the invention may determine
whether to allow the user equipment to join a IP multicast group by
deciding whether to route multicast traffic following a IGMP/MLD join
request from a user equipment to the network, based on requesting
authorization by the network. The request may use existing Gmb
Authorisation procedures, and in effect checks against a collision with
existing IP multicast addresses allocated for MBMS services.

[0093] Alternatively, it has been seen that the determination as to
whether or not to route the requested traffic may be based on static
information stored locally at the HNB 2, or in a database to which the
HNB 2 has access; the information may be stored in the local egress point
of the IP traffic in the local network, for example the L-GW 18.

[0094] In a variant of the embodiments, a message may be sent from the HNB
2 to the user equipment rejecting membership of the requested multicast
group, based on a determination that the address may be used by the
mobile operator's core network. That is to say, when it is determined
that collisions may occur between MBMS services and the IP multicast
group the user equipment requests to join, the HNB 2 rejects the request
by sending the related MBMS reject message, which appears as a service
reject to the user equipment.

[0095] It can be seen that according to embodiments of the invention, the
HNB will prevent the situation where user equipment that supports MBMS
multicast mode receives multicast packets from the LIPA network that are
unexpected while it was attempting to join an MBMS service using
Multicast Delivery Mode. This unexpected traffic would confuse or
possibly even crash the UE's multicast based client MBMS application.
Thus, embodiments of the invention ensure well-defined operation for UEs
that support multicast mode MBMS.

[0096] FIG. 4 illustrates a yet further embodiment of the invention, in
which it is first determined whether or not a multicast address is
present in a list of addresses of multicast groups relating to the first
data network, and if it is not, then a message is sent from the router
node to a serving node of the first data network requesting authorisation
to join the first multicast group. This approach will minimise
signalling, but has the advantage that it may be determined that the
first data network uses the first multicast address in the case that the
list is out-of-date.

[0097] Referring to FIG. 4, firstly a message is received from the user
equipment at the HNB 2 requesting membership of a first multicast group
having a first multicast address. Specifically, a IGMP join request for a
group G is received.

[0098] It may be determined whether the first multicast address is present
in a list of addresses of multicast groups relating to a mobile
operator's data network. Specifically, it may be determined whether or
not group G is in a static configured list of MBMS multicast mode
services.

[0099] If the determination is affirmative, then the HNB 2 inhibits
receipt of multicast traffic having the first multicast address from at
least a residential/enterprise network by the user equipment, by
discarding traffic having the multicast address received from the
residential/enterprise network, that is to say by not routing the
traffic. Specifically, the HNB 2 does not route traffic addressed to G
from the LIPA network to the user equipment. In a variant, the HNB 2 may
in addition not route traffic from the mobile operator's core network,
that is to say MBMS traffic, having the first multicast address to the
user equipment.

[0100] If the determination is negative, then the HNB 2 may send a message
to a serving node of the mobile operator's network requesting
authorisation to join the first multicast group. Specifically, the HNB
requests authorisation from the BM-SC 14 or authorisation server for the
UE 4 to use group G.

[0101] It may be then determined that a multicast group of the mobile
operator's network uses the first multicast address. This may be
determined on the basis of whether or not group G, in this example, is in
a static configured list of MBMS multicast mode services held, for
example, at a serving node of the mobile operator's network, for example
at the BM-SC 14.

[0102] If the determination is affirmative, then a message is sent from
the HNB 2 to the user equipment rejecting membership of the multicast
group. Specifically, the HNB 2 send a MBMS context activation reject
message to the user equipment.

[0103] If the determination is negative, then the HNB 2 routes traffic
from the residential/enterprise network to the user equipment, since it
has been determined that there has not been a clash of multicast IP
addresses between the mobile operator's network 4 and the
residential/enterprise network 6, that may be referred to as the LIPA
network. Specifically, the HNB 2 routes traffic from the LIPA network to
the UE 4.

[0104] In variants of embodiments of the invention, the first
determination of FIG. 4, that is to say whether the first multicast
address is present in a list of addresses of multicast groups relating to
a mobile operator's data network, may be omitted, and the process may
continue direct to the step of sending a message to a serving node of the
mobile operator's network requesting authorisation to join the first
multicast group.

[0105] In alternative embodiments of the invention, the HNB 2 may proceed
to route traffic from the residential/enterprise network to the user
equipment, on the basis of the first determination of FIG. 4, that is to
say whether the first multicast address is present in a list of addresses
of multicast groups relating to a mobile operator's data network.

[0106] FIG. 5 illustrates a principle of operation that may be used by
embodiments of the invention. At step 6.1, a join request relating to a
first multicast group having a first multicast group is received from a
user equipment 4 at a router node, typically a Home Node B2.

[0107] At step 6.2, it is determined whether or not the request is a
potential MBMS request, that is to say, it is determined whether or not a
mobile operator's core network to which the Home Node B is connected uses
the first multicast address for MBMS services, for example by consulting
a list of MBMS addresses that the first address is used by the operator's
core network, in particular as an address associated with a MBMS service.

[0108] If it does, then at step 6.4 the Home Node B 2 does not send a
message to the residential/enterprise network 6, that is to say the LIPA
network. In particular, it does not route a message to the LIPA network
requesting membership of the first multicast group. In addition, the Home
Node B may, in some embodiments of the invention, not route a message to
the mobile operator's core network requesting membership of the first
multicast group. The Home Node B may in addition send a message to the
user equipment 4 indicating that MBMS service is rejected.

[0109] If the determination at step 6.2 is negative, then at step 6.3 the
Home Node B may send a request to the home/residential network 6, i.e.
the LIPA network, requesting membership of the first multicast group.
Connection to the LIPA network may be made in the knowledge that the
request is unlikely to relate to an MBMS service in the operator's core
network.

[0110] FIG. 6 and FIG. 7 show in a schematic form an exchange of messages
according to embodiments of the invention.

[0111] In FIG. 6, it is determined at the Home Node B2 that there is
potential clash of multicast addresses between the residential/enterprise
network and the mobile operator's core network. As previously described,
this may be on the basis of a determination that a multicast group of the
first data network uses the first multicast address. On the basis of the
determination, a request to join a multicast group received from a user
equipment may be rejected, for example by sending a message to the user
equipment rejecting the request.

[0112] In FIG. 7, by contrast, it is determined at the Home Node B2 that
there is unlikely to be a clash of multicast addresses between the
residential/enterprise network and the mobile operator's core network. In
this case, a join requesrt may be passed to the LIPA network. The LIPA
network may, as applicable to the protocol employed, acknowledge or
authorise the join request. The Home Node B2 may then, if appropriate,
send a message to the user equipment 4 indicating that a multicast
service will be provided.

[0113] FIGS. 8, 9 and 10 illustrate methods that may be employed to
determine that a multicast group of the mobile operator's network uses
the first multicast address, and in particular that the first multicast
address is used in connection with a MBMS service.

[0114] FIG. 8 illustrates a method in which the Home Node B2 requests
authorisation to join a first multicast group, as a method of determining
whether or not a multicast group of the mobile operator's network uses
the first multicast address. If authorisation is received, then it is
determined that the first multicast address is used by the mobile
operator's network, and in particular it is assumed that the address is
used for a MBMS service. Alternatively, or in addition, the determination
may be made by consulting a list of multicast addresses relating to the
mobile operator's core network held at the Home Node B4, or accessible by
the Home Node B4. A message is sent to the user equipment 4 rejecting
membership of the multicast group. The message may be for example be a
MBMS context activation reject.

[0115] In FIG. 9, the determination as to whether or not a multicast group
of the mobile operator's network uses the first multicast address
proceeds as has been described in connection with FIG. 8, but inhibition
of receipt of traffic by the user equipment 2 from the mobile operator's
core network is achieved alternatively, or in addition to the method of
FIG. 8, by discarding multicast traffic, and in particular MBMS traffic,
received from the mobile operator's core network, preferably at the Home
Node B2. For example, a session start message may be discarded. A reject
message may be sent the the user equipment rejecting the join request as
described in connection with FIG. 8.

[0116] In FIG. 10, the determination as to whether or not a multicast
group of the mobile operator's network uses the first multicast address
proceeds as has been described in connection with FIG. 8, but inhibition
of receipt of traffic by the user equipment 2 from the mobile operator's
core network is achieved alternatively, or in addition to the methods of
FIG. 8 or 9, by sending a message cancelling the authorisation request to
the mobile operator's core network. The server system may send an
acknowledgement of the cancellation to the Home Node B2.

[0117] Similar methods to those described in connection to FIGS. 8, 9 and
10 may be used to inhibit receipt of traffic by the user equipment 2 from
the residential/enterprise network, dependent on the capabilities of the
network.

[0118] As already mentioned, inhibition of receipt of multicast traffic by
the user equipment 2 from either or both data networks may also be
achieved by not sending a request to join a multicast group of the
respective network.

INDUSTRIAL APPLICABILITY

[0119] The above embodiments are to be understood as illustrative examples
of the invention. It is to be understood that any feature described in
relation to any one embodiment may be used alone, or in combination with
other features described, and may also be used in combination with one or
more features of any other of the embodiments, or any combination of any
other of the embodiments. Furthermore, equivalents and modifications not
described above may also be employed without departing from the scope of
the invention, which is defined in the accompanying claims.